If it was a G3 iMac, I would install NetBSD. But it isn't. If I didn't already have half a dozen 9.1 machines, I would install 9.1. But the hypothetical situation has me owning a half a dozen 9.1 machines. Maybe some version of Mac OS 7 would interest me, but I'd rather do that on a 68k Mac to use my favourite version of System 7. That being 7.1. So I think that I would just end up searching for a new home for that PCI PowerMac.